The present invention relates to a conveyor including a travel path fitted with a friction drive for propelling a carriage supported in such a manner that the carriage can run on the travel path.
A carriage conveyor of this type includes a linear travel path for carriages, which is used as a means of constant-speed continuous conveyance in an assembly process for cars or the like. Each of the carriages includes a deck having a pair of side faces in parallel with the direction in which the carriages run. The drive for propelling the carriages on the linear travel path consists of frictional surfaces for drive and a friction drive wheel for carriage propulsion. The frictional surfaces are the side faces of the carriage decks. The drive wheel is located at the rear (start) end of a conveying path and engages compressively with the frictional surfaces. Each of the carriages pushes the preceding one.
The carriage conveyor also includes a return travel path for returning the carriages from the front end of the linear travel path to the rear end thereof. The front end of the linear travel path is connected to the rear (start) end of the return travel path by an outlet return path. The front end of the return travel path is connected to the rear end of the linear travel path by an inlet return path. Each of the outlet and inlet return paths may need to include a right-angle lateral travel path, which is fitted with turntables at both ends to turn the carriages. Alternatively, each of the outlet and inlet return paths may need to be fitted with a traverser on which a turntable for turning the carriages is mounted. This greatly increases the cost of equipment for turning the carriages.
The object of the present invention is to provide a carriage conveyor that can overcome the foregoing problem.
A carriage conveyor according to the present invention comprises a carriage travel path and a plurality of carriages. Each of the carriages includes a deck having a frictional surface for primary drive that is a side face formed on or near at least one of the right and left sides of the deck. The frictional surface is parallel to the direction in which the carriage travels. Each of the carriages further includes a bar fitted on the underside of its deck. The bar extends on the centerline of the deck. The centerline is parallel to the running direction. The bar has a side face forming a frictional surface for secondary drive. The carriage travel path includes a primary travel line and a secondary travel line. The primary travel line is a linear travel path, which is fitted with a drive for primary propulsion. This drive includes a friction drive wheel for compressive contact with the frictional surfaces for primary drive of the carriages. The secondary travel line is fitted with a plurality of drives for secondary propulsion, each of which includes a friction drive wheel for compressive contact with the frictional surfaces for secondary drive of the carriages. These drives for secondary propulsion are provided at intervals in the running direction.
On the primary travel line, which is a linear travel path, it is possible to strongly propel the carriages by the conventional method by frictionally driving their decks, which have sufficient strength. On the secondary travel line, it is possible to frictionally drive the carriages by using the frictional surfaces of the bars on the decks. The secondary travel line may include a curved travel path. When the carriages run on this curved travel path, the loci of their frictional surfaces for secondary drive do not deviate greatly from it. This makes it possible to propel the carriages smoothly along the curved travel path by merely constructing the friction drive wheel for compressive contact with the frictional surfaces for secondary drive in such a manner that this wheel can move to some extent laterally of the secondary travel line.
The primary travel line, which is a linear travel path, can be used for the heavy-load carriages loaded with articles. It is possible to freely, as the need arises, design the layout of the curved travel path, where it would be difficult to propel the carriages smoothly by means of a friction drive for use with the primary travel line. However, it is impossible in terms of strength to apply great frictional driving force in the secondary travel line. Therefore, the secondary travel line can be used as a return travel line for the unloaded light-load carriages. This return travel line may include a curved travel path incorporated suitably in it for turning the carriages while they are running. This removes the necessity for a turntable for turning the carriages or a traverser on which such a turntable is mounted. It is consequently possible to greatly reduce the cost for the whole equipment.
The drive for primary propulsion may be located at the rear (start) end of the primary travel line. The front end of the primary travel line may be fitted with a brake for preventing the carriages from running at a speed higher than a predetermined speed. The carriages conveyed into the primary travel line are propelled in order by the drive for primary propulsion at the rear end of this line. As a result, a train of carriages is present on the whole primary travel line, where all of them run at a constant speed, each of them pushing the preceding one. This makes it possible to use the primary travel line as a car assembly line or the like.
The bar on the underside of the deck of each carriage may be a middle bar fixed to a middle portion of the centerline of the deck. A front bar and a rear bar may be connected horizontally pivotally to the front and rear ends, respectively, of the middle bar. The front and rear bars do not protrude from the front and rear ends, respectively, of the deck. The bars form a bendable frictional surface for secondary drive on side faces thereof, which extends over substantially the whole length of the deck. A guide rail may be laid along the travel lines. Both ends of the middle bar and the free ends of the front and rear bars may each support a trolley in engagement with the guide rail. This makes it possible to shorten the radius of curvature of the curved travel path of the secondary travel line, and to lengthen the intervals between the drives for secondary propulsion on this line, further reducing the cost of equipment.
The specific structure and operation of the present invention will be understood easily from a preferred embodiment of the invention, which will be described below with reference to the accompanying drawings.